Multicomponent polymers

Babich VF, Lipatov YuS (1968) In Physico-chemistry of polymer multicomponent systems, Naukova Dumka, Kiev, p 222... 

By generalizing the above ideas to polydlsperse polymers (multicomponent mixtures), which should have many kinks in their adsorption isotherms, the reader will easily understand why isotherms of polydlsperse samples are usually rounded, the more so the wider the M distribution is. There are also consequences for the surface pressure, the layer thickness, and the interaction between polymer-covered surfaces. 

In practice, two-component solvent mixtures are employed as eluents and sample solvents inLC LC. One constituent of mixture supports elution of interactive polymer from the particular column, while another one induces its retention within column. To adjust polymer interactivity or to cope with the limited solubility of analyzed polymers, multicomponent solvents can be employed. Typical examples are mixtures of hexafluoropropanol with chloroform, which dissolve aromatic polyesters and some polyamides at ambient temperature. The sample solvents, eluents and barriers usually contain the same hquids but their composition is adjusted to fulfil their particular role Sample solvent must dissolve all its constituents and barrier must efficiently decelerate interactive macromolecules. Eluent serves either as a barrier in LC LCS, LC LCA and LC LCP or it promotes unhindered sample elution in LC LCD, LC LCU and LC LCI. 

Polymer materials are ubiquitous in our daily life. They often consist of more than one species of polymers and, therefore, can be called multicomponent systems, for example, polymer blends and block copolymers. Because of the repulsive interaction between the constituent polymers, multicomponent polymer materials often show phase separation. Organic-inorganic composites are another class of polymer-based multicomponent materials that have attracted considerable interest from researchers because they often exhibit unexpected properties synergistically derived from the constituents. Nanometer-sized particulate fillers, for example, carbon black (CB) and silica (Si) nanoparticles, are known to form hybrids with organic polymers, which show a significant increase in their static and dynamic moduli, strength, and thermal and electrical conductivities. 

Vol. 1 Polymer Engineering Vol. 2 Filtration Post-Treatment Processes Vol. 3 Multicomponent Diffusion Vol. 4 Transport in Porous Catalysts... 

Just as it is not necessary for polymer chains to be linear, it is also not necessary for all repeat units to be the same. We have already mentioned molecules like proteins where a wide variety of different repeat units are present. Among synthetic polymers, those in which a single kind of repeat unit are involved are called homopolymers, and those containing more than one kind of repeat unit are copolymers. Note that these definitions are based on the repeat unit, not the monomer. An ordinary polyester is not a copolymer, even though two different monomers, acids and alcohols, are its monomers. By contrast, copolymers result when different monomers bond together in the same way to produce a chain in which each kind of monomer retains its respective substituents in the polymer molecule. The unmodified term copolymer is generally used to designate the case where two different repeat units are involved. Where three kinds of repeat units are present, the system is called a terpolymer where there are more than three, the system is called a multicomponent copolymer. The copolymers we discuss in this book will be primarily two-component molecules. We shall discuss copolymers in Chap. 7, so the present remarks are simply for purposes of orientation. 

The growth of polyolefin fibers continues. Advances in olefin polymerization provide a wide range of polymer properties to the fiber producer. Inroads into new markets are being made through improvements in stabilization, and new and improved methods of extmsion and production, including multicomponent extmsion and spunbonded and meltblown nonwovens. 

As more complex multicomponent blends are being developed for commercial appHcations, new approaches are needed for morphology characterization. Often, the use of RuO staining is effective, as it is sensitive to small variations in the chemical composition of the component polymers. For instance PS, PC, and styrene—ethylene/butylene—styrene block copolymers (SEES) are readily stained, SAN is stained to a lesser degree, and PET and nylons are not stained (158,225—228). 

New product introductions are generally heavily supported by the technical service function. Many customers using chemical feedstocks to produce multicomponent products for the consumer market require extensive on-line evaluations of new raw materials prior to their acceptance for use. An example of this would be the use of a new engineering polymer for the fabrication of exterior automobile stmctural panels. Full-scale fabrication of the part foUowed by a detailed study of parameters, such as impact strength, colorant behavior, paint receptivity, exterior photodurabiHty, mar resistance, and others, would be required prior to making a raw materials change of this nature. 

Synthetic polymers have become extremely important as materials over the past 50 years and have replaced other materials because they possess high strength-to-weight ratios, easy processabiUty, and other desirable features. Used in appHcations previously dominated by metals, ceramics, and natural fibers, polymers make up much of the sales in the automotive, durables, and clothing markets. In these appHcations, polymers possess desired attributes, often at a much lower cost than the materials they replace. The emphasis in research has shifted from developing new synthetic macromolecules toward preparation of cost-effective multicomponent systems (ie, copolymers, polymer blends, and composites) rather than preparation of new and frequendy more expensive homopolymers. These multicomponent systems can be "tuned" to achieve the desired properties (within limits, of course) much easier than through the total synthesis of new macromolecules. 

Conducting Polymer Blends, Composites, and Colloids. Incorporation of conducting polymers into multicomponent systems allows the preparation of materials that are electroactive and also possess specific properties contributed by the other components. Dispersion of a conducting polymer into an insulating matrix can be accompHshed as either a miscible or phase-separated blend, a heterogeneous composite, or a coUoidaHy dispersed latex. When the conductor is present in sufftcientiy high composition, electron transport is possible. 

There are several approaches to the preparation of multicomponent materials, and the method utilized depends largely on the nature of the conductor used. In the case of polyacetylene blends, in situ polymerization of acetylene into a polymeric matrix has been a successful technique. A film of the matrix polymer is initially swelled in a solution of a typical Ziegler-Natta type initiator and, after washing, the impregnated swollen matrix is exposed to acetylene gas. Polymerization occurs as acetylene diffuses into the membrane. The composite material is then oxidatively doped to form a conductor. Low density polyethylene (136,137) and polybutadiene (138) have both been used in this manner. 

YOUNG, R, J., Introduction to Polymers, Chapman and Hall, London (1981) Multicomponent Polymer Systems, Advances in Chemistry Series No. 99, American Chemical Society, Washington (1971)... 

Bryk TM, Lipatov TE (1986) Physics and chemistry of multicomponent polymer systems, Haukova Dumka, Kiev, p 9... 

The situation becomes most complicated in multicomponent systems, for example, if we speak about filling of plasticized polymers and solutions. The viscosity of a dispersion medium may vary here due to different reasons, namely a change in the nature of the solvent, concentration of the solution, molecular weight of the polymer. Naturally, here the interaction between the liquid and the filler changes, for one, a distinct adsorption layer, which modifies the surface and hence the activity (net-formation ability) of the filler, arises. Therefore in such multicomponent systems in the general case we can hardly expect universal values of yield stress, depending only on the concentration of the filler. Experimental data also confirm this conclusion [13],... 

Sheer GE, Turner DT (1971) In Gould RF (ed) Multicomponent polymer systems, ACS, Wash. 

The interest in this type of copolymers is still very strong due to their large volume applications as emulsifiers and stabilizers in many different systems 43,260,261). However, little is known about the structure-property relationships of these systems 262) and the specific interactions of different segments in these copolymers with other components in a particular multicomponent system. Sometimes, minor chemical modifications in the PDMS-PEO copolymer backbone structures can lead to dramatic changes in its properties, e.g. from a foam stabilizer to an antifoam. Therefore, recent studies are usually directed towards the modification of polymer structures and block lengths in order to optimize the overall structure-property-performance characteristics of these systems 262). 

Equivalent expressions for equations (3) and (6) exist for the polymer (7). The Flory-Huggins expressions can also be extended to multicomponent systems (2) ... 

A similar expression can be derived for the polymer activity (11). The formalism can also be extended to multicomponent solutions (11). 

There are two types of multicomponent mixtures which occur In polymer phase equilibrium calculations solutions with multiple solvents or pol ers and solutions containing poly-disperse polymers. We will address these situations In turn. 

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